NC2. Advice on rust needed

[aliqut]

1. My model of MX-5 is: 1.8L 2010 NC
2. I’m based near: North Yorkshire
3. I’m looking for technical help or recommendations on: Rust treatment

Recently bought my first car, 2010 NC 1.8L! 110K miles. Based in the UK.

I’ve been driving it for about a month now, everything is mostly fine, aside from some issues shifting into 1/2/R, broken AC, and the rust.

I had a look at the underside at the local garage when I took the car in for a service, it didn’t look terrible, didn’t look great (I forgot to get any photos unfortunately). The mechanic told me it was pretty typical for its age. Mostly looked like surface rust, some flaking, but some of the underbody braces looked bad (I got some awful photos by sticking my phone under the car, attached to post, the rest of the car does not look this bad, from what I’ve seen at least), but these are bolted on and I plan to replace them later down the line.

My current plan is to treat the rust myself, since I’m on a tight budget. Buy the tools, jack the car up, take off the rear bumper, wheel arch liners, etc, wire brush as much rust off, spray with rust converter, then with Bilt Hamber Dynax-UB or the Dinitrol equivalent. I’m praying it won’t need any welding, the local mechanic didn’t seem to think it would need any.

My questions are:

• Is it worth the money I’ll have to put in for an MX-5 with 110K miles? Would it be more financially sensible to drive it till it falls apart instead? Try to sell it and buy another one?

• How effective can DIY rust treatment be really?

• Repair/maintenance costs in the long run. I bought the car for £2,500. At what point is it more reasonable to buy a new car rather than spend money on repairs. What if I put a bunch of money into fixing rust, other repairs etc and then the engine blows. I’m hesitant to spend any money fixing issues w the paint/on any basic mods knowing there’s rust lingering around.

I love this car a lot more than I thought I would, to the point where my girlfriend is starting to get jealous. I’d like to look after it properly.

Any advice would be appreciated. Thanks.

These images are the worst of it. The rest looks like its just got some surface rust, at least as far as I could tell.

Also, not sure if this is worth mentioning, but the entire MOT history contains no mention of underside corrosion… somehow.

[IanH]

A 16 year old MX-5, how long does the MOT have to run?

[MickAP]

It does look like that chassis rail is holed, it’s not the normal place for it to rot as bad as that. I’d be looking very closely in the rear lower wheel arches, they in part are covered by the wheel arch liner. Right under the car at the wheel arch meets sill too, a prone area to rot…..

Here, this pic wheel arch liner removed…

[aliqut]

It is MOTed till April.

[MX5-0912]

If you’re not too far from the south coast of England, I can recommend these guys: https://themx5restorer.co.uk/ they know the MX-5 inside-out and do free inspections on Saturday mornings. I had my car inspected and undersealed by them and I’m happy I did.

There should be other garages that know these cars well, elsewhere in the U.K..

The MX-5 rusts from the inside out and looking at that photo, it looks like rust is well established on the chassis rail.

P.s. just noticed you’re way up north.

[aliqut]

I plan on taking the wheels and arch liners off this weekend to see how bad it is. I’ll update this thread. What are my options if it is bad? Have I bought the wrong car?

[Wardy5]

@aliqut

It is MOTed till April.

If it’s only MOT’d until next month, I’d be minded to get the next test done promptly (it can be done upto 30 days in advance and still keep the same MOT anniversary date).

You can then get a better idea if it’s worth spending money on and what issues have been thrown up from an MOT perspective, before you spend further money.

However, looking at that one brief photo above, I’m surprised that a general comment regarding corrosion hasn’t been noted previously.

If you haven’t already, or if you haven’t been provided with all past MOT certificates, look up the MOT history. You can get a full rundown of where the previous tests were undertaken, by inputting details from the car’s V5 certificate:

Check the MOT history of a vehicle

[aliqut]

I have a slot booked to get the car MOTed early, it expires end of April, I’m taking it in around the end of this month.

I’ve already looked through the entire MOT history, I did before I bought the car. Not a single mention of corrosion, and no major issues. It’s why I’m so surprised it’s this bad. Definitely wont be buying another MX-5 without examining the underside. Lesson learnt I guess.

[Wardy5]

Have all the MOT tests occurred at the same test station?

[IanH]

It’s always good advice to buy an MX-5 from the underside up. I’ve seen many people seduced by shiny coachwork to later find out it needs substantial rust correction work.

There’s a couple of possible scenarios

The MOT comes back clean and it’s only superficial. Invest some time cleaning it up and enjoy the car.

The MOT comes back and it’s structural affecting the safety of the car. Can you patch it to pass and run it for a year with the expectation it’s a parts donor at the end of it.

If it’s the second I wouldn’t be making a significant investment to save a car if this age, the money you would spend could be put into a cleaner car and avoid the headache of chasing repairs.

[Goodj]

Buying the car for £2500 should have been the red flag.

Essentially you made a down-payment against a pile of future invoices.

However, if you were to pour the money into it, you then know it’s solid. Buying another car could leave you in the same situation

[Wicked93gs]

Take it from someone who has restored a 50+ year old car where I had to replace about 70% of the sheet metal: “Rust Converter” is a gimmick that is absolutely useless. Rust is iron oxide…formed from 3 things: water, iron(or steel in this case) and oxygen. You can’t “convert” rust into something its not…its rust, you aren’t magically going to change its chemical structure by spraying it with something, after spraying it, it will still be iron oxide. That being said….once you get rid of the existing rust(wire brush, sandpaper, cutting and welding in new steel, whatever) you can most certainly prevent more rust from forming by covering the surface of the steel with a surface coating such as paint, or bedliner, or whatever. Now, that is not to say all surface coatings are created equal…far from it. The thicker a surface coating is, the more prone to de-lamination and air pockets(and therefore rust) it is. As an example: I would never put any type of undercoating on a panel I wanted to protect from rust…nor would I use sound deadener on that panel for the same reason: Both are thick “coatings” prone to air bubbles that will trap moisture in if ever exposed to it…and we all know water has a way of getting everywhere it possibly can through the smallest of gaps. No…the way you protect from rust is start with a good quality epoxy primer on bare metal(most will require an industrial air compressor and proper spray gun to apply, but there are 2-part epoxy primers available in rattle-cans available just for this type of job, but those cans are typically only 75% the coverage of a regular can). After the epoxy primer, you lay down whatever paint system you are using…whether that is a single stage paint like older lacquer paints, or base coat+clear coat. Being the underside of a car, it will inevitably have the paint damaged from chips rocks flung at the undercarriage from the tires, etc. The way around this is to simply make undercarriage paint touch-up part of the maintenance of the car, along with washing the undercarriage free of any salt or grime on a regular basis. That is how you maintain a car to keep the rust away….there is no magic band-aid to fix rust….you have to remove/replace and prevent. I have learned this the hard way…if you do not, then its only a matter of time until the rust eats the car. This is also acceptable if you are fine with the realization that the car is going to have a limited lifetime.

[aliqut]

@Wardy5

Have all the MOT tests occurred at the same test station?

No, believe it or not. Different centre every year or two.

@Goodj

Buying the car for £2500 should have been the red flag.

Really? I thought £2500 was within the average price range for a 1.8L NC2, with a PRHT.

@Goodj

Essentially you made a down-payment against a pile of future invoices.

However, if you were to pour the money into it, you then know it’s solid. Buying another car could leave you in the same situation

So it is worth pouring money into in your opinion? I’d like to be able to drive it for another say, 5 years. If it falls apart after that, I’d be content. I could realistically save up to get the car professionally restored, but that would likely take me at least 6 months.

@Wicked93gs

you lay down whatever paint system you are using…whether that is a single stage paint like older lacquer paints, or base coat+clear coat.

Something like Hammerite Direct to Rust? Also, being a novice, and being on a tight budget, would it be okay to get as much rust off as I can, and go ahead with the epoxy primer + paint on top of any sections that clearly need to be cut out, and leave the welding for another time, say, 6-12 months? Would that slow down/halt the rust?

Thank you all for the help and advice, I really appreciate it.

[Wicked93gs]

Realistically from the picture you posted, I see rust pinholes in the frame to the left of(and likely under) where the sub-frame attaches. This indicates that the metal has rusted through entirely. Even if you remove all the rust from the bottom side and coat it…the inside of the frame rail will still have a compromised surface(pitting is rust) and compromised strength. Will it slow the rust down? Sure, it will slow it down by 50%, but its going to still be there until it is patched….and to make things worse, after you get it patched, you still have to find some way to paint it from the inside of the frame rail or the process will just start again(and no, weld-thru primer is not a solution…the process of welding burns the primer away, its a zinc coating that is meant to applied to a fresh weld, not prior to welding). You still paint the back side of the patch as much as possible before welding, but you can still expect the weld bead itself to have burned away any paint within an inch or two during welding. There are small sprayer tips meant for spraying inside frame rails, or you can make your own from something as simple as plastic tubing with holes poked in the sides…but no matter how you do it, painting inside of frame rails is a blind process. The times I have done frame rail patching were on cars that I could actually get to the inside from the end of the frame rail, but from my perspective its never been that much of a problem if you have a MIG welder(and other fab tools), some steel, and the time to work on the car. At this point, I just expect to have to to do rust repair to old cars like any other repair. In areas where salt destroys cars…don’t get attached to a car unless you can repair rust(or have a friend who can) because it quickly becomes more expensive than the car is worth.

Now, after all that gloom and doom: If I had to rate your rust damage on a scaled of 1 to 10, it would rate about a 3 to me. Requires repair, but not bad enough to justify getting rid of the car yet. The crossmember is in worse shape than the frame rails.

[MisterG1]

Hello again

I think the two green circles are where it looks like the metal is perforated. Maybe clutching at straws, but I’m not convinced it is: It looks to me like they are holes in a layer of detached underseal, rather than holes in the (undoubtedly rusty) metal. You won’t really know until you can get under the car and have a scrape at it.

The orange arrows are where the underseal is peeling back, and is (IMHO) typical of what happens on MX5s. It really needs scraping off, and I’d expect you to find more rusty metal underneath.

The areas in the red circles show rust staining, and are also probably hiding rust scabs - again scrape it off. It’s possible that these are holes emerging from the inside.

I would try and remove the brace (to give you a clear run) and clean the area up (i.e scrape off all the loose material and get back to metal if you can). If it hasn’t perforated, and is rusting on the outside, remove as much rust as you possibly can by mechanical means (angle grinder with knotted or twisted wire brush and/or stripping disc) and apply rust converter to what ever rust that’s left. Paint it well (epoxy) and keep an eye on it. It will buy you a year or two - more if you do it well, and keep it maintained. You will then be in no worse situation than you are now (in this area, anyway!!).

I’ll stress that you need to remove the rust if at all possible. Rust converters only buy time IMHO, and they only do this if you’ve already got rid of most of the rust.

Ideally replace the brace with a better condition one from a breaker / aftermarket rather than waste time and effort trying to clean it up.

If the metal has perforated, it could well be an MOT fail, if within 300mm of where the subframe braces mount.

You could probably get an ‘MOT’ standard welded repair fairly cheaply, but be aware that this is often done by welding a sheet of metal over the holes. It then means that the car passes the current MOT, but it locks in all the old rust and moisture, meaning that the corrosion under the patch carries on regardless - possibly quicker than it would have done otherwise. This leaves a much more extensive area of rust and a bigger, more difficult repair that may well prove uneconomic down the line. The better way to do it is to cut out the rusted metal and let in new pieces, paint everything and use cavity “wax” of some sort, but that costs more.

My 2p

Good luck!

Edit to add: Take a look at the whole of the car. If this is the only area of rust, then it makes some sense to address it. If the whole of the underside of the car is in that state, then you may be better off cutting your losses.

[Belle427]

Looks quite bad to me, I can bet when you start cleaning it up it will gradually start to hole and when that happens your screwed really as it just gets bigger.

As said you would need to remove the brace to get good access.

I would not use a converter on it personally, you can buy more powerful rust removal solutions but i cant comment on how good they are.

[MX2000]

For your own safety I would take it to somewhere with a good reputation and get an MOT test as soon as possible. You need to understand what you’ve got. Then get an estimate of the work required and decide on your next step.

[MickAP]

The two holes circled can be as you say, just flaky underseal. My concern and I’ve had it on my NC previously, just under in that picture the two holes is a flexible heat shield, that’s held in place by those plastic pop rivets (tree) type clips. On mine it started to rust around the clip holes, I had to remove the shield partially and grind back the surface rust and then paint. I put some new clips in and also removed and painted that cross member, it was rusty under and around the fixings for that too.

[Nurburg]

In my opinion (and I’m no expert) it’s always worth trying to restore where you can.

Get a wire brush set for your drill and just go gently on the worst bits and then just keep going. You’ll then start to see if / where any problem areas are. I agree you can’t convert rust, but you can slow it and prevent it (damn hard on the MX-5 though).

If you come across a piece that needs replacing, then as long as it’s not structural, welding can be done quite cheaply. We had the rear sill welded for £50.

Good luck, don’t loose heart.

[aliqut]

Thank you everyone for the advice and suggestions, it means a lot.

I’m taking the car to an MX-5 specialist nearby, just to assess how bad the condition of the entire car is, and to get a chance to look more closely at the underside while its up on ramps. After that, I’ll decide whether or not it’s worth saving up to get everything repaired properly.

I will wire brush off and paint whatever I can, just to buy myself some time. I’m also asking around my local area, looking for a garage I could rent. Sounds like learning to weld is going to be worth it in the long run.

I’ll update this thread with my next steps.

Again, thank you all!!